753 research outputs found
A Scale-Explicit Framework for Conceptualizing the Environmental Impacts of Agricultural Land Use Changes
Demand for locally-produced food is growing in areas outside traditionally dominant agricultural regions due to concerns over food safety, quality, and sovereignty; rural livelihoods; and environmental integrity. Strategies for meeting this demand rely upon agricultural land use change, in various forms of either intensification or extensification (converting non-agricultural land, including native landforms, to agricultural use). The nature and extent of the impacts of these changes on non-food-provisioning ecosystem services are determined by a complex suite of scale-dependent interactions among farming practices, site-specific characteristics, and the ecosystem services under consideration. Ecosystem modeling strategies which honor such complexity are often impenetrable by non-experts, resulting in a prevalent conceptual gap between ecosystem sciences and the field of sustainable agriculture. Referencing heavily forested New England as an example, we present a conceptual framework designed to synthesize and convey understanding of the scale- and landscape-dependent nature of the relationship between agriculture and various ecosystem services. By accounting for the total impact of multiple disturbances across a landscape while considering the effects of scale, the framework is intended to stimulate and support the collaborative efforts of land managers, scientists, citizen stakeholders, and policy makers as they address the challenges of expanding local agriculture
Lattice Calculation of Point-to-Point Hadron Current Correlation
Point-to-point correlation functions of hadron currents in the QCD vacuum are
calculated on a lattice and analyzed using dispersion relations, providing
physical information down to small spatial separations. Qualitative agreement
with phenomenological results is obtained in channels for which experimental
data are available, and these correlation functions are shown to be useful in
exploring approximations based on sum rules and interacting instantons.Comment: 11 page
Dopamine D 4 Receptor-Deficient Mice Display Cortical Hyperexcitability
The dopamine D(4) receptor (D(4)R) is predominantly expressed in the frontal cortex (FC), a brain region that receives dense input from midbrain dopamine (DA) neurons and is associated with cognitive and emotional processes. However, the physiological significance of this dopamine receptor subtype has been difficult to explore because of the slow development of D(4)R agonists and antagonists the selectivity and efficacy of which have been rigorously demonstrated in vivo. We have attempted to overcome this limitation by taking a multidimensional approach to the characterization of mice completely deficient in this receptor subtype. Electrophysiological current and voltage-clamp recordings were performed in cortical pyramidal neurons from wild-type and D(4)R-deficient mice. The frequency of spontaneous synaptic activity and the frequency and duration of paroxysmal discharges induced by epileptogenic agents were increased in mutant mice. Enhanced synaptic activity was also observed in brain slices of wild-type mice incubated in the presence of the selective D(4)R antagonist PNU-101387G. Consistent with greater electrophysiological activity, nerve terminal glutamate density associated with asymmetrical synaptic contacts within layer VI of the motor cortex was reduced in mutant neurons. Taken together, these results suggest that the D(4)R can function as an inhibitory modulator of glutamate activity in the FC.Fil: Rubinstein, Marcelo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de Investigaciones en IngenierĂa GenĂ©tica y BiologĂa Molecular "Dr. HĂ©ctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cepeda, Carlos. University of California at Los Angeles; Estados UnidosFil: Hurst, Raymond S.. University of California at Los Angeles; Estados UnidosFil: Flores Hernandez, Jorge. University of California at Los Angeles; Estados UnidosFil: Ariano, Marjorie A.. The Chicago Medical School; Estados UnidosFil: Falzone, Tomas Luis. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de Investigaciones en IngenierĂa GenĂ©tica y BiologĂa Molecular "Dr. HĂ©ctor N. Torres"; ArgentinaFil: Kozell, Laura B.. Oregon Health Sciences University; Estados UnidosFil: Meshul, Charles K.. Oregon Health Sciences University; Estados UnidosFil: Bunzow, James R.. Oregon Health Sciences University; Estados UnidosFil: Low, Malcolm J.. Oregon Health Sciences University; Estados UnidosFil: Levine, Michael S.. University of California at Los Angeles; Estados UnidosFil: Grandy, David K.. Oregon Health Sciences University; Estados Unido
Increased desmin expression in hindlimb muscles of aging rats
Abstract Background Aging skeletal muscle frequently exhibits a reduction in force produced per unit muscle tissue, variously termed muscle quality, specific tension or dynapenia. Muscles from animals in which desmin expression is reduced exhibit similar properties, raising the possibility that reduced desmin expression contributes to impaired force production in aging muscles. Methods We examined expression of desmin and synemin, both intermediate filament proteins, in the plantarflexor muscles of adult (6-8 months) and older (24 months) rats. We have previously reported age-related reductions in muscle quality and sarcoplasmic reticulum function in these animals. Results Significant effects of age and muscle were found for the expression of desmin (P= 0.040 and <0.001 respectively), but not synemin. Desmin expression was increased in the aging muscles, with the greatest changes observed in the gastrocnemius muscles. Muscle quality, but not muscle mass, was reduced in the aging plantarflexor muscles. Conclusions Loss of desmin does not account for reduced force production in aging muscles. The potential effects of the age-related increase in desmin on muscle function remain unclear, but may include dissipation of contractile force
Soil microbial biomass and function are altered by 12Â years of crop rotation
Declines in plant diversity will likely reduce soil microbial biomass, alter
microbial functions, and threaten the provisioning of soil ecosystem
services. We examined whether increasing temporal plant biodiversity in
agroecosystems (by rotating crops) can partially reverse these trends and
enhance soil microbial biomass and function. We quantified seasonal patterns
in soil microbial biomass, respiration rates, extracellular enzyme activity,
and catabolic potential three times over one growing season in a 12-year crop
rotation study at the W. K. Kellogg Biological Station LTER. Rotation
treatments varied from one to five crops in a 3-year rotation cycle, but
all soils were sampled under a corn year. We hypothesized that crop diversity
would increase microbial biomass, activity, and catabolic evenness (a measure
of functional diversity). Inorganic N, the stoichiometry of microbial biomass
and dissolved organic C and N varied seasonally, likely reflecting
fluctuations in soil resources during the growing season. Soils from
biodiverse cropping systems increased microbial biomass C by 28–112 % and
N by 18–58 % compared to low-diversity systems. Rotations increased
potential C mineralization by as much as 53 %, and potential N
mineralization by 72 %, and both were related to substantially higher
hydrolase and lower oxidase enzyme activities. The catabolic potential of the
soil microbial community showed no, or slightly lower, catabolic evenness in
more diverse rotations. However, the catabolic potential indicated that soil
microbial communities were functionally distinct, and microbes from
monoculture corn preferentially used simple substrates like carboxylic acids,
relative to more diverse cropping systems. By isolating plant biodiversity
from differences in fertilization and tillage, our study illustrates that
crop biodiversity has overarching effects on soil microbial biomass and
function that last throughout the growing season. In simplified agricultural
systems, relatively small increases in crop diversity can have large impacts
on microbial community size and function, with cover crops appearing to
facilitate the largest increases
Correlation Functions of Hadron Currents in the QCD Vacuum Calculated in Lattice QCD
Point-to-point vacuum correlation functions for spatially separated hadron
currents are calculated in quenched lattice QCD on a lattice
with . The lattice data are analyzed in terms of dispersion
relations, which enable us to extract physical information from small distances
where asymptotic freedom is apparent to large distances where the hadronic
resonances dominate. In the pseudoscalar, vector, and axial vector channels
where experimental data or phenomenological information are available,
semi-quantitative agreement is obtained. In the nucleon and delta channels,
where no experimental data exist, our lattice data complement experiments.
Comparison with approximations based on sum rules and interacting instantons
are made, and technical details of the lattice calculation are described.Comment: 31 pages in REVTeX (with 10 figures to be added using figures
command), MIT CTP #214
A review and comparative study of release coatings for optimised abhesion in resin transfer moulding applications
In this study, a number of abhesion promoting coatings were considered in terms of their physicochemical and release properties. The techniques used to further this study include; FEGSEM, AFM, profilometry, AFM, XPS, AES, SSIMS, FTIR and contact angle analysis for coating physical and chemical characterisation along with PF-AFM and other adhesion and mechanical tests to determine surface release properties. These coatings were applied to metal substrates and were based upon silicone, fluoropolymer or metal-PTFE composite chemistry, all being potentially useful as release films for resin transfer moulding (RTM) applications. The semi-permanent Frekote B15/710 NC mould release coating system, which is based on PDMS, proved extremely effective in terms of release against a cured epoxide applied under pressure. Although fluoroalkylsilane coatings offer a number of technological advantages for release applications they generally produce very thin coatings which conform any existing surface topography and adhesion through mechanical interlocking occurs. The commercial PTFE-based coatings were found to provide poor release properties due to the presence of surface microcracks which allowed epoxide penetration when cured under elevated pressure and temperature. Electroless Ni/PTFE composite coatings comprise hard nickel-phosphorus matrix containing a very fine dispersion of PTFE particles. The matrix proved sufficiently robust for industrial applications and the low friction and surface energy provided by the embedded PTFE combined with macroscopic scale surface roughness provided efficient mould release
The Three Neurogenetic Phases of Human Consciousness.
ABSTRACT This paper is an organization and conceptualization of a genetic account of human consciousness and to establish an initial list of the neurogenetic correlates of consciousness (NgCC). This will be accomplished by establishing networks of genes that are involved in the multiple facets of the process of human consciousness. The methodology utilized in this work is the evaluation of a small number of genes that have been researched experimentally in order to understand their role in brain development and function. The results demonstrate that most neurogenetic genes can be categorized into three phases: the emergence of neuron-based consciousness, the continuum of neuron-based consciousness, and the neurodegeneration of consciousness. This work also revealed that some genes have a function in more than one of the neurogenetic phases. As of now a starting point has been established in terms of identifying some NgCC but there is room for expansion as there are likely to be hundreds of more genes that have yet to be identified or the function pertaining to human consciousness has not yet been fully understood
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